Clonidine Suppression Test (Three-hour)

Casandra

Casandra Test Code LC70027Version 1 (DRAFT)

Performing Lab

Lab LabcorpLab Test ID 123133CPT Code 82384

Clonidine Suppression Test (Three-hour)

Also known as: Adrenaline, Plasma, Epinephrine, Plasma, Noradrenaline, Plasma, Norepinephrine, Plasma, Plasma Catecholamines

Clinical Use

Order Test

Use

Diagnose pheochromocytoma and those paragangliomas that may secrete epinephrine, norepinephrine, or both. Such tumors may cause paroxysmal or persistent hypertension. Investigation of hypertensive patients, especially younger individuals, particularly when hypertension is paroxysmal, suggesting pheochromocytoma.2

Special Instructions

Several medications can prevent clonidine suppression and should be discontinued 48 hours before collection if possible. These include β-adrenergic blockers, tricyclic antidepressants, and thiazide diuretics. α-adrenergic blocking agents do not interfere with clonidine suppression. The patient should abstain from smoking and avoid certain foods and medications prior to the test. An indwelling heparinized catheter is preferred to avoid stress-induced catecholamine elevation during venipuncture.

Limitations

Plasma levels are useful if elevated during or immediately following a hypertensive episode, but false-negatives can occur if the specimen is drawn during an uneventful period. Normotensive pheochromocytoma has been reported. False-positive results are common and can be influenced by various factors including certain drugs and extrinsic conditions such as cold or hypoglycemia.

Test Details

Methodology

Chromosomal / Cytogenetics (HPLC with electrochemical detection)

Biomarkers

Epinephrine

Analyte

Epinephrine, Plasma (Baseline, 2-hour, 3-hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Norepinephrine

Analyte

Norepinephrine, Plasma (Baseline, 2-hour, 3-hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

Total Catecholamines

Analyte

Catecholamines, Plasma Total (Baseline, 2-hour, 3-hour) • Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order Codes

1464-7
1606-3
1388-8
1462-1
1604-8
16558-9
1463-9
1605-5
16559-7

Result Turnaround Time

2-4 days

Specimen

Plasma

Volume

3 mL each for baseline, two-hour, and three-hour specimens

Minimum Volume

2.2 mL each for baseline, two-hour, and three-hour specimens

Container

Chilled lavender-top (EDTA) tube

Collection Instructions

Draw blood in chilled lavender-top (EDTA) tube. Invert tube for thorough mixing with preservatives. Centrifuge at 4°C. Transfer plasma to labeled plastic transport tubes and freeze immediately at -20°C. Ship frozen. Tubes should be prelabeled 'Baseline', 'Two-hour', 'Three-hour'. Separate frozen specimens for additional tests.

Patient Preparation

Abstain from smoking, walnuts, bananas, and certain medications. Use of an indwelling heparinized catheter is recommended. The patient should remain recumbent during the collection process.